"Shameless" films in Chicago twice a year, including this month in the North Lawndale neighborhood and on North Michigan Avenue, usually for five days at a time. These shots are mixed in with interior scenes and the occasional exterior scene filmed in the LA area to create a show that feels as "Chicago" as the four other series that call Chicago home without actually filming here year round.

It sounds simple, but it's not.

"The actors really have to come prepared and understand we'll shoot a piece of Episode 7 in the morning and then get in a van and go across town and shoot a piece of Episode 12," said "Shameless" co-executive producer and former "ER" associate producer Michael Hissrich. "It's kind of astonishing. It's brutal at times, but so rewarding."

This begs the question: Why not avoid the hassle and film the entire series in Chicago?

"We had a desire to shoot the entire series here," Hissrich said of the show, which stars Oscar-nominated actor William H. Macy and Emmy Rossum. "But because the talent involved didn't really want to relocate full time, we devised a way to do this much like it was done on 'ER.' We built a set to do some location work in LA and used neighborhoods that look older and have some brick architecture. We knew from our experience on 'ER' that if we have those scenes mixed in with real Chicago scenes, we can get away with it."

TV shows tend to film for longer periods than films, which means they have a greater economic impact on the city than even a blockbuster movie (the longer productions film here, the more local actors and crews they employ and the more local products they buy and rent). Illinois Film Office director Betsy Steinberg said 2012 was the first year that Chicago had four TV shows filming in the city in their entirety in one year.

That number very well could have been six. "The Good Wife" opted not to film here for the same reason as "Shameless."

"('Good Wife' star) Julianna Margulies had it written into her contract with CBS that she would not go more than a half-hour outside of New York because she has a small child," Steinberg said. "That's one of those issues where there's no way around it. But in the case of 'Boss,' Kelsey Grammer was willing to relocate to Chicago part of the year."

The Chicago-set "ER," which starred George Clooney and, coincidentally, Margulies, ran on NBC for 15 seasons from 1994 to 2009. The medical drama shot mostly at Warner Bros. Studios but visited Chicago four times a year to film exteriors.

"The fact is that travel to Chicago added expenses, but we deemed it to be creatively necessary," said former "ER" executive producer Christopher Chulack. "Sometimes it did get complicated shooting for four or five episodes during one trip. Sometimes the script wasn't fully done or written. Sometimes we had to shoot a shot in Chicago five weeks ahead of (the next scene) in LA. We would film a scene in Chicago that had to match the majority of the episode ahead of time. That was interesting, but you adapt."

"The lead actors and writing staff live in Los Angeles and have families there," Chulack said. "It's tough to relocate your family. Also, Chicago has almost everything, but there are expenses other than travel. That's why states like Illinois and North Carolina give rebates on every dollar spent. And in Hollywood, you know you will have no problems with stage space or any problems finding specialty makeup houses. You lose that sort of access in cities other than Hollywood."

Of course, many series have managed to make it work. In addition to the shows currently filming in Chicago, the city has hosted the first season of Fox's "Prison Break," CBS' "Early Edition" and short-lived shows such as A&E's "The Beast," Fox's "Chicago Code" and NBC's "The Playboy Club." The Denis Leary-produced firefighter comedy pilot, "Sirens," recently filmed on location in Chicago and at Cinespace Chicago Film Studios on the Near West Side, and is waiting to see if it will get picked up by USA Network.

"Chicago Fire" — which also revolves around firefighters — recently earned a full season pickup from NBC. The producers of the show said the decision to shoot entirely in Chicago was an easy one.

"I think when you're deciding where to shoot a show, the ideal situation is to shoot the show where it's set," "Chicago Fire" co-executive producer Peter Jankowski said. "If you do 'Law & Order,' you should shoot in New York — unless it's 'Law & Order: LA.' So that's where you start. When finances get involved in the decision-making, you maybe find yourself shooting exterior scenes on location and the bulk on soundstages. In the case of 'Chicago Fire,' it was really a simple decision. As you can tell, Chicago is such a personal character in the show. Filming it in Los Angeles wouldn't ring true. You can't get that shooting in the studio."

Jankowski said "Chicago Fire" — from "Law & Order" and "Miami Vice" creator Dick Wolf — had no problem convincing its actors to move to Chicago for filming. But it also helps that the cast features less-established actors.

"Getting actors to go there is not an issue," Jankowski said. "In fact, I think it's a selling point. Maybe it's because we have a younger cast. … We had shows in New York for 20 years, so it's refreshing now to have Chicago in our blood."

Starz has yet to officially announce if it will bring back "Boss" for a third season, which means "Shameless" is the only series that filmed in Chicago in recent years that has made it past two (Season 3 of "Shameless" premieres Jan. 13).

"It's absolutely a victory (for Chicago)," Steinberg said of "Shameless." "The fact is that we're still getting people working on the show. And it's not just for the week they're here. They put people to work weeks in advance (to set up the shoot). Of course, it would be great if they shot the entire show here. It's a great show. But we'd rather have it than not have it."